Chordata Bateson, 1885 - chordates
   Class Elasmobranchii Bonaparte, 1838 see Infraclass Elasmobranchii Bonaparte, 1838
     Subclass Selachii see Division Selachii
       Order †Ichthyotomi (Cope)
         36 Family †Xenacanthidae Geinitz, 1860
         37 Family †Cladodontidae Giebel, 1846 see Family Ctenacanthidae Bonaparte, 1850, "nom. praeval."
         38 Family †Chondrenchelyidae Jordan, 1923 [monotypic]
         39 Family †Gyracanthidae Woodward, 1906